docs: def change_dir():
      """Change the local directory if the HADOOPY_CHDIR environmental variable is provided"""
      try:
          d = os.environ['HADOOPY_CHDIR']
          sys.stderr.write('HADOOPY: Trying to chdir to [%s]\n' % d)
      except KeyError:
          pass
      else:
          try:
              os.chdir(d)
          except OSError:
              sys.stderr.write('HADOOPY: Failed to chdir to [%s]\n' % d)